Metal-containing catalysts are used in a large number of processes in the manufacturing and processing of thousands of tons per day of industrial chemicals, chemical intermediates, automotive exhausts, plastics and petroleum products to name a few. Such catalysts typically contain a majority of one or more valuable and expensive metals including such metals as platinum, vanadium, palladium, silver, copper, cobalt, manganese, nickel and molybdenum. Such catalysts may contain one or more of these and other metals in pure form or as compounds such as oxides, hydrogenated and organic metal compounds, with or without halides, or inorganic residues such as silica, alumina, calcium, magnesium, or sulfur.
As is well know, over time in use, such catalysts become spent, primarily from poisoning. In processes using such catalysts, it is necessary to periodically replenish the catalyst. There is great need for recovery of the metals fraction of spent catalyst, both in terms of cost savings and also for conservation of such metals. However, to date, such catalysts metal recovery processes are inefficient and expensive, indeed if they are in use at all.
Currently, two methods are primarily used for handling of cobalt/manganese metal and hydrogen bromide from waste catalyst streams from PTA/DMT manufacturing plants. When the waste is incinerated, only about 80% of the cobalt is recovered, the bromine is lost and the processing cost is very high. Also, the vent gas is heavily laden with dioxins which are extremely dangerous to the environment. Settling ponds can be used to treat the catalyst waste stream, but are disfavored or outlawed due to the potential for pollution. Other methods such as ion exchange processes, or distillation and extraction processes, have been used unsuccessfully for handling catalyst waste streams from PTA/DMT manufacturing plants.